They MAY ask you which certificate you would prefer, but don't bet on it. I was asked which I would prefer (for the Dash-8) and I told them the Mesa cert, as opposed to the freedom certificate. I was given the Mesa dash, however some people in my class were not asked or given a choice.
Beyond that, however, you fill spots where ever they need you. I bid DEN 1st, but as the 2nd most junior guy in my dash class, I was awarded my 3rd choice.
Be advised that DEN is a dash base only. The jet guys in my class went to Dulles. I think the 2 most senior guys in the class got ORD. PHX is extremely senior.